1. Field of the Invention
The present invention relates to a progressive distributor for lubricants which are fed via a joint channel under pressure successively to several output points. The progressive distributor comprises at least two successively connected piston bore elements with each having a piston which is provided with control grooves and can be slipped between two end positions in the cylinder bore. The piston subdivides the cylinder bore into two outer metering chambers and at least one intermediate control chamber.
2. Brief Description of the Background of the Invention Including Prior Art
Such progressive distributors for lubricants are known for example, from the German Patent Applications Laid Out Nos. 1,475,550, 1,902,587 and 2,437,473. The lubricant fed to such a progressive distributor via a joint channel under pressure and running into individual metering chambers is distributed via the pistons successively to individual lubricating locations. In this case, the pistons mutually control each other such that discharge of the lubricant of the piston of the second piston element is provided after discharge of the lubricant via the piston of the first of the successively connected disk-like piston elements. Then, another new lubricant discharge via the piston of the first piston element follows the discharge of lubricant via the piston of the second piston element. In particular, the relatively long connection channel between the metering chamber of the second piston element and the metering chamber of the first piston element can result in operating disturbances in case of such a progressive distributor since a part of the lubricant disposed in the connection channels is only moved back and forth.
In particular, in cases of lubricants with high penetration, the results are hardening or, respectively, bleeding of the lubricant. The same disadvantage also occurs in case of a change of the lubricant. This results finally in such a large flow resistance that the distributor becomes blocked. Furthermore, enclosed air can hardly be removed in these distributors, which also results in interferences with the functioning of the apparatus. Due to the fact that in the case of the known progressive distributors the lubricant leaves the metering chamber in each case via the same channel by which it is fed into the metering chamber, the connection channel up to the metering chambers includes dead zones where no exchange of the lubricant occurs. The piston of each individual piston element carries at its three front faces in each case a stepped tenon, which on one hand determines the final position of the piston in each case and which assures on the other hand that a pressure effective surface is available at the piston for allowing the lubricant to flow in. Contact surface can result at the beginning in delays based on the so called "adhesive effect". In case of high operation frequencies, the pistons, or respectively, their tenons, result in considerable contact noise since no damping of the final positions occurs.
A progressive distributor is known from the German Patent Application Laid Open DE-OS No. 2,917,883 where the individual cylinder bores are disposed relative to each other such that the connection channels can be kept short and, in particular, can be kept at equal length. This reduces the passage flow resistance and assures that lubricant is not moved back and forth in the connection channel. However, this is associated with the precondition that the volume in the connection channels is smaller than the metering volume. Very small metering volumes thus cannot be realized with such a distributor while maintaining the above mentioned advantages. The other indicated disadvantages of the known progressive distributors are however also present in this distributor. Included air cannot escape based on the compressibility.
In addition, the progressive distributor with the short connection channels requires a high expenditure for installation. A later occurring change in the number of the lubricant output bores is not possible in this case.